1. Field of the Invention
The present invention concerns an optical fiber cable.
2. Description of the Prior Art
An optical fiber cable provides means for protecting one or more optical fibers therein, both during the manufacturing process and during subsequent installation and service conditions. The design of the cable must prevent excess tensile load from being supported by the optical fibers; otherwise static fatigue over a period of time can lead to breakage of the optical fibers. In addition, lateral loads must be resisted to provide for crush resistance of the cable. It is also desirable to provide for waterproofing of the cable. In some designs, this takes the form of an air core, which can be pressurized with a dry gas to prevent water entry. More recently, a trend has developed towards so-called "filled cables" wherein a filling compound is located in the interstices of the cable to prevent water entry and migration. One requirement that is of great importance in optical fiber cables is that significant compressive strains be avoided on the optical fibers themselves during the manufacturing process or during the installation and service life of the cable. Significant compressive forces can cause buckling of the optical fibers, resulting in increased losses due to microbending of the fibers.
It is apparent that the above considerations place significant constraints on the choice of materials, designs, and manufacturing processes required to simultaneously meet the above requirements. It is desirable to obtain cable designs that provide protection against a variety of external forces and influences, thereby retaining the low loss characteristics of the optical fibers therein.